Most of us have heard the term Hybird picking. It's also known as Chicken Pickin'.
Hybrid picking is a guitar-playing technique that involves picking with a pick and fingers at the same time. It therefore allows guitar players who use a pick (plectrum) to perform music which would normally require fingerstyle playing. It also facilitates wide string leaps (e.g. from the fifth string to the first string, etc) which might otherwise be quite difficult. The technique is not widespread in most genres of guitar playing (though notable exceptions exist, see below), but is most often employed by country/bluegrass flatpickers who play music which occasionally demands fingerstyle passages.
Players who use hybrid picking generally hold the pick in the traditional grip, i.e., between the forefinger and thumb. Since this only involves the use of two fingers, it leaves three fingers of the picking hand free, which is what allows for hybrid picking.
Hybrid picking allows a picking guitarist to play some things otherwise impossible; however, there are limitations to the technique. The primary issue stems from the angle at which the free fingers must pick the strings. While a player who only uses his or her fingers to pluck the strings (e.g., a classical guitarist) holds their hand at such an angle that the fingers travel perpendicular to the strings, allowing for a clear attack, a player holding the pick naturally positions their hand such that the pick strikes perpendicular to the strings, putting the fingers in a position almost parallel to the strings. This makes the attack of the free fingers of a hybrid picking guitarist considerably weaker than that of a purely fingerpicking guitarist, unless significant changes are made to the hybrid picker's hand position. The angle of the fingers for a hybrid picker also limits the speed at which fingerpicked notes can be played, though speed can be achieved as normal using the plectrum.